Characteristics of Solid-Liquid Two-Phase Flow in Deep Sea Mining Pipelines

The technical feasibility of the pipeline hydraulic lifting system has been confirmed through multiple offshore trials and it has been currently the most promising deep-sea mining system. When transporting minerals collected from the deep-sea seabed to the sea surface along with seawater, complex multiphase flow upwelling issues are generated. In this paper, in terms of the open-source Computational Fluid Dynamics (CFD) software OpenFOAM®, a Lagrangian solver coupled the Eulerian and Lagrangian phases is established to simulate the flow of solid-liquid two-phase within a vertical riser. In this model, the discrete phase is solved by using the Discrete Element Method (DEM), and the continuous phase is achieved by solving the Navier-Stokes (RNAS) equations, taking into account the complex particle interaction. The movement of solid particles in turbulent flow is calculated and the distribution of solid particles under different conditions is obtained. The flow characteristics of solid-liquid two-phase flow are obtained from the perspectives of internal flow field distribution. The results demonstrate that the established numerical model for solid-liquid two-phase flow is relatively reliable, and the transported flow velocity has a certain impact on the lifting performance of the riser. This research offers a theoretical basis and practical reference for the future design of pipeline lifting systems.